1. Field of the Invention
The present invention relates to a vehicle body frame for a motorcycle which includes a head pipe for steerably supporting a front fork which pivotally supports a front wheel and a steering handle. A pair of left and right main frames extends rearwardly and downwardly from the head pipe with a down frame extending rearwardly and downwardly from the head pipe at an angle steeper than an angle at which the main frames extend rearwardly and downwardly.
2. Description of Background Art
A vehicle body frame for a motorcycle is disclosed in JP-A-2007-8434. In this body frame structure, front end portions of the main frames are joined to an upper portion of the head pipe, and a front end portion of the down frame is joined to a lower portion of the head pipe.
In the vehicle body frame disclosed in the above-mentioned JP-A-2007-8434, the head pipe, the main frames and the down frame are firmly connected to each other by forming a truss. Accordingly, torsion and vibrations in the lateral direction from a front wheel are directly transmitted to a vehicle body frame side. Thus, it is necessary to increase the rigidity of whole vehicle body frame and the rigidity of mounting portions of parts or the like to be mounted on the vehicle body frame.